CVE-2021-24440

Sign-up Sheets <= 1.0.13 - Stored Cross-Site Scripting

2021-06-21 00:00

Strategic Overview

Status: Patched in 1.0.14
Affected Plugin: Sign-up Sheets
Affected Version: < 1.0.14
CVSS: 4.8Medium
Weakness type: CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE: CVE-2021-24440

At a glance

CVE-2021-24440 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Sign-up Sheets WordPress plugin, affecting versions < 1.0.14. It carries a CVSS score of 4.8 (reachable over the network; low attack complexity). The issue is fixed in version 1.0.14; sites on affected versions should update now. Disclosed June 2021, reported by Ajay Sandipan Thorbole.

Vulnerability Overview

The Sign-up Sheets WordPress plugin before 1.0.14 did not sanitise or escape some of its fields when creating a new sheet, allowing high privilege users to add JavaScript in them, leading to a Stored Cross-Site Scripting issue. The payloads will be triggered when viewing the 'All Sheets' page in the admin dashboard

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed.

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Reaching this weakness in Sign-up Sheets < 1.0.14 takes a caller who can reach the endpoint. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.

Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For Sign-up Sheets the fix is 1.0.14: builds < 1.0.14 are affected, anything from 1.0.14 onward is not.

Remediation

Update to version 1.0.14, or a newer patched version

How does WordSec protect against this?

The attempt arrives as an ordinary request to Sign-up Sheets: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Sign-up Sheets 1.0.14 closes this, and updating the plugin is the step that ends it.

Firewall
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2021-24440 https://www.wordfence.com/threat-intel/vulnerabilities/id/f371feb6-93ae-4759-ab44-d58106093290 https://nvd.nist.gov/vuln/detail/CVE-2021-24440

Related records

Same weakness class

6.1CVE-2024-6020: Sign-up Sheets <= 2.2.12 Reflected Cross-Site ScriptingCVE-2024-6020

Other vulnerabilities in Sign-up Sheets

CVSS Vector

4.8

CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredHigh
User InteractionRequired
ScopeChanged
ConfidentialityLow
IntegrityLow
AvailabilityNone

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